U.S. Pat. No. 5,267,673 describes a pump of the above type. In that known pump, the membrane comprises a portion disposed on the outer side of the wall defining the outlet passage and is deflected from it under the effect of an overpressure in the pump chamber.
With such a configuration, the fluid is not dispensed along the pump axis, which can be a problem when the pump is intended to be mounted over a distribution nozzle.